Disclosure statement

Stefan H. Doerr receives funding from NERC and The Leverhulme Trust

Cristina Santin receives funding from the Leverhulme Trust.

António Bento Gonçalves does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

In one tragic week, many dozens died in two seemingly unconnected fires in the UK and Portugal. One blazed through a high-rise building in London, far away from natural ignitions and cladded with what should have been non-flammable insulation. The other was a wildfire, suggested to have been started by lightning, which then engulfed rural communities surrounded by highly flammable forest plantations.

Yet the two tragedies share parallels, and not only in the search for answers. Both fires spread quickly and burned with an intensity well beyond what firefighters were able to stop. Both caught residents largely unprepared, with their escape routes cut off, and both left a death toll far beyond what might have been expected for either a building or a forest fire in such highly-developed countries.

Indeed, the fires in Portugal claimed 64 lives, making it the country’s deadliest wildfire in recorded history.

The fires broke out in central Portugal on June 17 and burned for several days.Paulo Novais / EPA

Potential ignition sources for fires are common, be they lightning, accident or arson. However, advances in fire detection, firefighting and use of less flammable building materials have led to a much lower threat from fires in modern cities. The same cannot be said for the rural communities in north-central Portugal and indeed many other regions of the Mediterranean.

The tinderbox of Europe

The roots of Portugal’s latest fire can be found in economic and social changes. Over the past few decades, the country’s rural areas – already among Europe’s poorest regions – have seen significant depopulation as residents moved to wealthier cities or countries in search of work, leaving behind almost abandoned villages. As a result, a landscape that was once dominated by farming, grazing and open oak forest land, has been replaced with denser vegetation such as plantations of native pine (Pinus pinaster) and, more recently, Australian eucalyptus (Eucalyptus globulus).

Both trees grow fast and provide valuable timber. In theory, they are lower maintenance, and require fewer workers, than the more open and intensely managed agri-forest of the past. Such plantations therefore sound like a sensible option for the region.

However, the switch to pine and eucalyptus also resulted in a much more flammable landscape. In fact, Eucalyptus globulus, introduced in many countries for pulp production, is one of the world’s most flammable tree species and its extent has more than doubled in Portugal since the 1980s. In severe forest fires, burning bits of vegetation (firebrand) are often lifted by wind and can travel hundreds of metres. Eucalyptus bark is particularly effective at spreading fire in this way.

The humid Atlantic climate of the northwestern Iberian peninsula also plays a role. Mild winters with high rainfall allow for excellent growing conditions, yet its dry, hot summers combine to make this region the tinderbox of Europe.

Impossible to extinguish

Forest fires are therefore common in this region and Portugal has one of the best fire detection and fighting capabilities in Europe. But though its average annual area burned has decreased in recent years, this tragic fire has been a stark reminder that the threat remains.

Firefighters are well aware that once a fire spreads in dense vegetation, such as pine or eucalyptus forests, in hot and windy conditions, it is essentially impossible to extinguish. Efforts are then typically aimed, not always successfully, at halting its spread at its flanks and onto infrastructures, or aiding the evacuation of residents. In the mountainous terrain of Portugal with few escape routes and the fires’ spread accelerated by firebrand igniting new areas ahead of the fire front, this can become an impossible task.

Most victims died in their cars when flames overtook them.Paulo Novais / EPA

The scale of human losses in this fire has been unprecedented in Portugal’s recent history, yet the occurrence and extent of fire is not. What caused the fire could be seen as almost immaterial as there will always be potential ignition sources, particularly in areas with widely scattered population. Whether fire will spread and pose a risk to people is then a matter of vegetation flammability, terrain and weather, along with the level of planning and effective communication required to quickly move residents to safe areas.

In this event, hot dry weather, scattered villages with a dwindling population insufficiently prepared for fire, surrounded by steep terrain with extensive monocultures of highly-flammable trees and insufficient communication, combined into a tragic loss of life. Yet, as with London’s Grenfell Tower fire, the high fire risk was far from unforeseeable. There is much that can be done to reduce the threat from, or even eliminate, highly flammable materials – be it insulation around buildings, or dense forest plantations surrounding villages. In both cases, importants lessons must be learned.